class_docstr: Uses mock policy for 4x4 gridworldenv
  '4x4': [
      'SFFF',
      'FHFH',
      'FFFH',
      'HFFG'
  ]
  0: left
  1: down
  2: right
  3: up
  -1: no move
  'S' : starting point
  'F' or '.': free space
  'W' or 'x': wall
  'H' or 'o': hole (terminates episode)
  'G' : goal
  [2,2,1,0,3,1,1,1,2,2,1,1,1,2,2,1]
code: def test_ray_batch_sampler(self, ray_local_session_fixture):
      del ray_local_session_fixture
      assert ray.is_initialized()
      workers = WorkerFactory(
          seed=100, max_episode_length=self.algo.max_episode_length
      )
      sampler1 = RaySampler(
          self.policy, self.env, worker_factory=workers
      )
      sampler1.start_worker()
      sampler1.shutdown_worker()
  
file_path: garage/tests/garage/tf/samplers/test_ray_batched_sampler_tf.py
imports: from unittest.mock import Mock
  import ray
  from garage.envs import GridWorldEnv, GymEnv
  from garage.np.policies import ScriptedPolicy
  from garage.sampler import RaySampler, WorkerFactory
  from tests.fixtures.sampler import ray_local_session_fixture
label_desc: Use image node_id 3 for calling the TestRaySamplerTF obj's underlying member method code with example usage: obj.test_ray_batch_sampler(ray_local_session_fixture) without return types